Physical quantity measuring devices have been known as means for measuring physical quantity (e.g. pressure) of fluid to be measured.
Examples of the typical physical quantity measuring device include a pressure sensor unit having a pressure sensor held by holders (Patent Literature 1: JP-B-5499169).
In Patent Literature 1, the holders include a first holder provided with a flange that holds an end of the pressure sensor near an opening and a second holder provided with a flange that holds an end of the pressure sensor near a diaphragm, where the first holder is a component independent of the second holder.
As another example of the physical quantity measuring device, a measurement/display unit including: a casing; a vibration sensor disposed on a bottom of the casing; and a support mechanism disposed inside the casing and provided with a fixing claw for fixing the vibration sensor on the bottom has been disclosed (Patent Literature 2: JP-A-2005-214843).
In Patent Literature 2, the support mechanism is made of a plastic material or the like. The fixing claw is integrated with the support mechanism.
Still another example of the typical physical quantity measuring device includes a sensor attachment mechanism including: a sensor body; and an attachment portion on which the sensor body is attached, the attachment portion being attached to a cylindrical portion (Patent Literature 3: JP-A-2004-325210).
In Patent Literature 3, the attachment portion is made of a synthetic resin and includes: a flange surrounding an outer circumferential portion of the sensor body; a pair of attachment pieces attached to the flange; and an engagement claw provided to each of the attachment pieces, the engagement claw being engaged with an engagement hole provided on the cylindrical portion.
In Patent Literature 1, since the first holder and the second holder are independent components, the number of the components and, consequently, production cost increases. In addition, since the pressure sensor is mounted on the flange of the first holder and the pressure sensor is covered with the second holder from a side near the diaphragm and pressed by the flange of the second holder in assembling the pressure sensor unit, the sensor assembly process becomes complicated.
The device disclosed in Patent Literature 2 is configured to measure vibrations, not pressure. Accordingly, it is not necessary to provide a joint provided with a port for delivering the fluid to be measured toward the sensor module, and thus a structure for attaching the sensor module to the joint is not disclosed.
In Patent Literature 3, since the attachment portion attached to the sensor body is attached to the cylindrical portion, an additional step for attaching the attachment portion to the sensor body is required. In addition, since the engagement hole has to be formed on the cylindrical portion, the strength of the cylindrical portion per se may be decreased. Supposing that the cylindrical portion corresponds to the joint, a hole in the joint in addition to the pressure inlet may result in decrease in strength of the joint.